Navigation Performance Assessment with an Automotive Receiver Exploiting OSNMA and FDE
Antonio Angrisano, Messina University; Domenico Di Grazia, Fabio Pisoni, Giovanni Gogliettino, Domenico Rega, STMicroelectronics; Salvatore Gaglione, Parthenope University; Ciro Gioia, Independent Researcher
Date/Time: Wednesday, Sep. 18, 11:48 a.m.
Introduction and State of the Art
The Galileo Open Service Navigation Message Authentication (OSNMA) is an open access free of charge service based on the provision authentication capabilities, allowing the users to confirm that the received navigation data originated has not been modified [1]. The OSNMA protocol data are transmitted through the Galileo I/NAV navigation message on E1-B signal. Currently, OSNMA data are provided for 20 Galileo satellites. According to OSNMA info note, the target market segments of the service are numerous including agriculture, aviation, maritime. Among the market segments, a specific use case is the one related to automotive applications. Several applications will benefits from OSNMA capabilities, for example: Road User Charging (RUC) enables toll operators to charge a user (i.e., vehicle) based on its authenticated position, for the use of the roads and for traffic and congestion control. Also insurance companies could exploits OSNMA for pay as you drive services, in which the users pay the insurance fees as a function of the actual usage of the vehicle. A specific user case is the smart digital tachograph, which leverages Global Navigation Satellite System (GNSS) positioning to support road enforcers, by recording the position of the vehicle at different points during the working day. For this specific case, the EU regulation [2] is already in force, its current consolidated version was published in August 2023. The implementing regulation not only specifies that the use of authenticated GNSS and its authentication capability is compulsory, when available but it specifically foresees that GNSS receiver shall have the capability to support OSNMA. Automotive applications are usually carried out in urban environments, where the buildings limit satellites reception making more challenging the authentication process. In these scenarios, the multipath phenomenon could lead to inaccurate position solution, several approaches are currently available to mitigate the effect of outlier; in this study we focus on Receiver Autonomous Integrity Monitoring (RAIM) to identify and reject measurements affected by gross errors.
The potential of the service has attracted the attention of research groups and industrial partners. Several scientific papers, analysing different aspects of OSNMA, have been published. During the public observation phase, OSNMA-ready receiver performance has been analysed in [3]; in [4], a methodology for supporting the implementation of the protocol and assessing the OSNMA-related performance in different environment conditions was presented. The observed operational information and performance indicators of a ten-day-long dataset collected in static open-sky conditions in southern Finland is discussed in [5], the assessment was carried out using OSNMALib [6].
Added value of the paper
Large part of the work in the specialised literature focused on the analysis of the performance in static conditions and in good signal reception scenarios (open-sky). For automotive users no analysis is currently available, and in this context, several aspects could impact the authentication performance: not only the receiver will be dynamic but also the signal conditions could vary significantly. In addition, in urban canyons, single or multiple outliers could make the navigation solution inaccurate if not un-feasible. Currently, no studies have been performed to investigate the impact of OSNMA on RAIM algorithms. The performance of RAIM algorithms is strongly affected by the available redundancy, hence the exclusions of not authenticated satellites could lead to reduced RAIM performance. This aspect has not been investigated in the specialised literature. For the assessment, different tests have been carried out using OSNMA ready receiver developed by ST Microelectronics; the receiver has been equipped with a specific firmware enabling Galileo OSNMA functionalities. The authentication protocol is implemented on the receiver following the current OSNMA documents. The device is able to verify OSNMA authentication and provides a flag for the authenticated satellites.
The tests have been performed, using the automotive devices provided by ST-Microelectronics in static and dynamic conditions and in different environments including open-sky and urban scenarios. The performance is evaluated at different levels, starting from the number of authenticated signals passing to the RAIM specific indicators (protection levels and capability to identify and rejects outliers). Finally, the impact on the position accuracy is evaluated for the horizontal and vertical channels; statistical parameters of the errors such as mean, standard deviation and 95th percentile are computed, considering the solutions with and without OSNMA, with and without RAIM. For the analyses, a customized navigation algorithm has been developed, the navigation engine exploits measurements provided by the Teseo V receiver and the associated authentication flag. The Teseo V receiver was developed in the framework of the Patrol project. The STM Teseo V chip with firmware co-developed by STM and FDC, the device implements algorithms to protect the integrity of OSNMA assets against jamming, spoofing and other security concerns, with applications in the area of smart tachographs and potentially beyond [7].
Setup and Preliminary Results
Three setups for the tests have designed and implemented, in all the cases the Teseo V was used. For the static tests, two different locations were used one for open-sky analysis and one for obstructed scenarios, the data were collected simultaneously. For open-sky conditions, the reference coordinates of the antenna were computed using long data collection processed using Real TIme Kinematic (RTK); in the obstructed scenario, the presence of outlier and the partial obstruction of the sky makes the GNSS alone solution more challenging. For these reasons, the position of the antenna was computed using topographical approach exploiting total station measurements allowing a centimetre level accuracy. For the obstructed static case two hours of data were collected in the Centro Direzionale di Napoli using the Teseo V receiver with a specific firmware able to process OSNMA.
For the dynamic tests, a van was used, it was equipped with different grade devices: a high-grade GNSS antenna mounted on the roof connected via a splitter to a high hand and to an automotive device. The dynamic tests were performed in different scenarios including highway (without signal obstruction and with higher speed) and city centre where the presence of obstacles limits the satellites visibility and the vehicle speed is reduced. The estimation of the true path is of paramount importance when the position accuracy achieved by receivers or positioning algorithms is the main metric to be assessed. To this aim a high-grade platform combining GNSS and an Inertial Measurement Unit (IMU) and high accuracy Post Processing Kinematic (PPK) capabilities based combining raw measurements from the professional receiver in rover and base configuration is used.
Preliminary results for some specific devices in kinematic conditions have been already analysed. In terms of solution availability in open-sky scenarios, it has been observed that the availability of the solution is very high for all the considered configurations. For dynamic and obstructed tests, the presence of obstacles and multipath errors severely impact the navigation performance in both cases using all the satellites or using only authenticated satellites.
Bibliography
[1] European Commission, "Galileo Open Service Navigation Message Authentication (OSNMA) Signal In Space Interface Control Document (SiS ICD)," European Union, 2023.
[2] European Commission, "Commission Implementing Regulation (EU) 2016/799," European Union, 2016.
[3] M. Nicola, B. Motella, M. Pini and E. Faletti, "Galileo OSNMA Public Observation Phase: Signal Testing and Validation," IEEE Access, vol. 10, pp. 27960-27969, 2022.
[4] L. Cucchi, S. Damy, M. Paonni, M. Nicola, B. Motella and I. Fernandez-Hernandez, "Assessing Galileo OSNMA Under Different User Environments by Means of a Multi-Purpose Test Bench, Including a Software-defined GNSS Receiver," in Proceedings of the 34th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2021), St. Louis, Missour, 2021.
[5] T. Hammarberg, J. García, J. Alanko and M. Bhuiyan, "An Experimental Performance Assessment of Galileo OSNMA," Sensors, 2024.
[6] A. Galan, I. Fernandez-Hernandez, L. Cucchi and G. Seco-Granados, "OSNMAlib: An Open Python Library for Galileo," in Navitech, Northwich, 2022.
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